1. Field of the Invention
The present invention relates to a semiconductor device using a semiconductor chip, and particularly to a semiconductor device including a semiconductor chip bonded to a die pad and packaged with a molded portion made of a synthetic resin.
2. Description of the Related Arts
Generally, a light emitting diode lamp of the type described above includes an insulating substrate in the form of a chip, on which a die pad and a pair of first and second electrode terminals all of which are made of a metal film are formed so that the die pad is electrically connected to the first electrode terminal. The device further includes a semiconductor chip bonded to the die pad and electrically connected to the second electrode terminal.
To bond the semiconductor chip to the die pad electrically connected to the first electrode terminal in the semiconductor device, a thermally meltable die bonding material such as solder paste is used. Specifically, an appropriate amount of such die bonding material is applied to an upper surface of the die pad, and then the semiconductor chip is placed on the die bonding material. In this state, the die bonding material is once melted by heating and then hardened.
Conventionally, although the die pad has a rectangular configuration which is similar to the rectangular configuration of the semiconductor chip, the die pad is made considerably larger than the semiconductor chip to be bonded thereto, which causes the problems described below.
In bonding the semiconductor chip to the die pad, it is necessary to bond the semiconductor chip at or near the center of the die pad. However, when the die bonding material applied to the die pad is melted, the semiconductor chip is floated on the melted die bonding material, and the die bonding material spreads largely to all sides over the upper surface of the die pad. Therefore, in accordance with the spreading of the die bonding material to all sides, the semiconductor chip in the floated state moves along the upper surface of the die pad to be away from the center. Thus, when the die bonding material is hardened thereafter, the semiconductor chip is fixed to the die pad at a position offset from the center. Moreover, when the semiconductor chip is put on the die pad at an offset position, the semiconductor chip is fixed at the offset position of the die pad without correction.
Moreover, in bonding the semiconductor chip to the die pad, it is necessary to arrange the semiconductor chip so that each of the corners of the semiconductor chip is oriented in a predetermined direction. However, since the semiconductor chip floated on the melted die bonding material can rotate freely, each of the corners cannot be oriented in a predetermined direction. Thus, the semiconductor chip is fixed with the orientation of the corners deviated.
The positional deviation from the center and deviation of the corner orientation of the semiconductor chip may hinder the connection of a metal wire to a predetermined electrode of the semiconductor chip in electrically connecting the semiconductor chip to the second electrode terminal by wire bonding or may cause such a connection failure that an intermediate portion of the metal wire comes into contact with the semiconductor chip. Further, to package the semiconductor chip with a molded portion made of a synthetic resin, the molded portion need be made relatively large in view of the above-described two kinds of deviation, which leads to an increase in size and weight of the semiconductor device.
Particularly, when the semiconductor device is an LED device using a LED chip as a semiconductor chip, the position of the light source and the directionality of light emitted from the LED chip changes due to the positional deviation from the center and deviation of the corner orientation of the LED chip, so that variation of the directionality of light is large.